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Re: [Xen-devel] Contiguous DMAble memory in Dom0 user space linux proces

To: "Kashmira. K." <chimnee@xxxxxxxxx>
Subject: Re: [Xen-devel] Contiguous DMAble memory in Dom0 user space linux process
From: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Date: Wed, 13 Jan 2010 16:31:53 -0500
Cc: winterfi@xxxxxxxxx, xen-devel@xxxxxxxxxxxxxxxxxxx
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On Wed, Jan 13, 2010 at 01:03:39PM -0800, Kashmira. K. wrote:
> Hello Xen experts,
> 
> I am trying to get contiguous DMAble memory in user space application which 
> is a processes running on xen capable Linux.

Why? Is the driver you are communicating with doing DMA of huge chunks of 
memory (bigger than 2MB?)

There surely must be another way to make your application do what it has
to do than allocating such a large swath of memory.


> Is it possible to use the  HYPERVISOR_grant_table_op hypercall passing 
> GMTTABOP_map_grant_ref as command to achieve this. If so, to use this 
> hypercall the grant reference is required. How do I get the grant reference?  
> Would appreciate if I can get an example code or pointer to one to clearly 
> understand how to achieve this.

Grant reference won't get you contiguous memory. It will get you memory
shared between domains.


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